The present invention relates to an excavation-roof support, such as is for instance used in mining applications.
Roof supports of this general type are well known, and are basically composed of a base from which a shield extends upwardly at one side towards the face of the excavation. The shield is supported by a pit prop or the like, and at its free end it carries a roof-supporting cap which is intended to bridge the distance between the face of the excavation and the base, since the base as a general rule cannot be moved close to the excavation face where space is required for conveyors or other equipment. In many instances, the height of the roof of an excavation will vary within a substantial range, for example in mining with the thickness of a vein of coal or the like may increase or decrease as a mining gallery is being driven deeper into the ground. This presents difficulties when, as already mentioned earlier, it is desired to maintain the front end of the roof supporting cap at a certain spacing from the face of the excavation, since the pivot axis between the free end of the shield and the cap is always located on an arc in the different elevational positions of the cap, which arc surrounds the pivot where the shield is mounted on the base. Since this pivot is usually relatively close to the floor of the excavation, it follows that, as the roof of the excavation recedes from the floor from point to point, the spacing between this pivot and the cap may vary widely, and consequently, the spacing between the front edge of the cap and the face of the excavation will similarly vary. Such support structures cannot, as pointed out earlier, be moved close to the face of the excavation because conveyors and other equipment must be located immediately adjacent the face, so that in areas where the roof is relatively high, there will be a very dangerous gap between the front edge of the roof supporting cap and the face, where the roof may break in since it is not supported by the cap.
The prior art has mostly proposed to provide separate supporting structures for each roof height in excavations, so that if the height of the roof of an excavation increased or decreased significantly, from a preceding location in the same excavation, a new support structure had to be brought in and installed.
A proposal in the prior art to accommodate a single support structure to varying roof heights required a construction which is difficult to use in actual operation, and is relatively complicated.
The need for a support structure of the type in question, capable of being adjusted in the manner suggested above, is therefore undiminished until now.